Separating ED Patient Flow from Workflow

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In an ED we need enough space to accommodate people and enough capacity to do the work safely, as well as respond to surges in patient arrivals and surges in workload. A simple model of the ED from the perspective of the health professionals working in ED considers the workload associated with the arrival of each new patient into the ED care area. A simple one stock model from the literature is shown below.

Causal Loop

To remove the confusion about whether patients or work (or both) are arriving and departing, I have modified the model to explicitly show the flow of patients and the flow of work. I have also split capacity into two types, work capacity and space capacity. Now for each patient in ED a new amount of (expected) work hours required to process that patient is added to the workload stock. The workload stock is sometimes called a backlog of orders or a todo list. It can be thought of as all the todo lists in the ED and includes the whiteboard of things to do and the implicit and explicit tasklists of all the staff.

Fig. 1 - Patient flow is NOT Workflow [Source]

(from Wears and Perry resilience)

This simple view shows that patients arrive add to the workload and when the workload is completed the patient leaves. Of course there are other additions to the workload such as equipment maintenance and routine reporting and sometimes workload is completed after the patient leaves, such as radiologist reporting of medical imaging studies.

Rich Picture Version

Fig. 2 - Space and Work in ED [Source]
Fig. 3 - Space and Work in ED with Space Effects unfolded [Source]

Here I have added additional causal links to show some of the potential causal feedback loops in the interaction between space effects and work rate effects on the flow of patients and work. Can you label some of the loops and add additional links and loops to the picture?

Fig. 4 - Space and Work in ED completely unfolded [Source]


See also Responses to Service Work Pressure for more detailed general discussion of work effects on departure rate.

Questions & Comments to Geoff McDonnell
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